When discussing the Mk 18 / CQBR program, we can divide the history and discussion in to two distinct categories: 1) The weapon system itself / upper receiver supplied and 2) the group of accessories deployed on said weapon systems (SOPMOD).

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Mk 18 Mod 0 / CQBR

The M4 carbine and M16 are not ideally suited for all missions, so it was proposed that the modularity of the M16 series would allow a user to replace the upper receiver of an existing weapon with one more suitable to the task. One of two proposed special mission receivers that were planned for inclusion into the SOPMOD Block II kit, the CQBR has taken off on its own. Like the proposed Special Purpose Receiver, the Close Quarters Battle Receiver has been more or less taken on by the Naval Surface Warfare Center, Crane Division (often referred to as NSWC-Crane or just "Crane") as its own project following the CQBR's removal from the SOPMOD program. Just as the Special Purpose Receiver morphed into the Special Purpose Rifle, and was type-classified as Mk 12 Mod 0/1, the complete CQBR-equipped carbine has been type-classified as the Mk 18 Mod 0.

The purpose of the CQBR remains to provide operators with a weapon of submachine gun size, but firing a rifle cartridge, for scenarios such as VIP protection, urban warfare, and other close quarters battle (CQB) situations. The CQBR is designed to provide improvement over previous AR-15/M16-type weapons in this category. The CQBR is usually issued as a complete weapon system, and not just an upper receiver. The CQBR was once only available to Naval Special Warfare units, but the Mk 18 Mod 0 has become general issue for Visit, Board, Search, and Seizure (VBSS) missions and, as of 2006, for NCIS agents deploying to active combat zones.[citation needed] The Mk 18 is also used by the Coast Guard's Tactical Law Enforcement Teams, Maritime Safety and Security Teams, and Maritime Security Response Team and the United States Navy's Explosive Ordnance Disposal (EOD) Operators.

Wikipedia has a good article with sources on the original CQBR/Mk 18 Mod 0 and its development.

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SOPMOD

The SOPMOD Program Management Office at NSWC Crane, IN, provides standardized, versatile weapons accessories to meet needs across SOF mission scenarios. These accessories increase operator survivability and lethality by enhanced weapon performance, target acquisition, signature suppression, and fire control.

The CQBR itself was originally part of the SOPMOD program as an accessory replacement upper receiver for the M4. However it was eventually separated out into its own project.

SOPMOD accessories for the M4/CQBR originally included things like the KAC RIS/RAS, SOPMOD stock, KAC M4QD suppressor, AN/PEQ-2 illuminator/laser, ECOS-N red dot, ACOG, etc

The SOPMOD program has gone through multiple minor and major evolutions throughout its lifetime. The most significant is commonly defined as "Block II" and included the introduction/replacement of accessories that met the updated needs of operators. The most visually significant "Block II" accessory is probably the replacement of the KAC rail/FSB with the  Daniel Defense RIS II free float rail with low-profile gas block. Other updates include things like the Surefire SOCOM sound suppressor, EOTech RDS (553/SU-231 & EXPS 3-0/SU-231a), LA-5/PEQ ATPIAL, etc

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Link to docs and photo albums

 Presentation on CQBR from Crane
 Operator's Manual for Mk 18 Mod 0
 SOPMOD Program Overview presentation from Crane
 Photo Album of Mk 18 Mod 0
 Photo Album of CQBR with SOPMOD Block II accessories

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Because of the long history of both the CQBR/Mk 18 and SOPMOD programs, it's common to find weapons with various mixed configurations in the field, all depending on what time and unit the weapon system belongs to. Below are a few examples with descriptions to illustrate this.


Example of a Mk 18 Mod 0 in as-issued configuration including: M16A1 surplus lower receiver, SOPMOD buttstock, KAC RIS, KAC M4QD flash hider, Aimpoint Comp M2 in Wilcox mount, LMT rear fixed sight, CQD rear sling plate.


NSW Operator CQBRs with original SOPMOD accessories including KAC M4QD sound suppressor and AN/PEQ-2 IR Illuminator/Laser.


Member of a Combat Camera team with a CQBR with KAC RAS and M4QD flash hider but with other updated accessories from the "Block II" SOPMOD kit including SU-231a (EOTech EXPS 3-0), EOTech G33 Magnifier, LA-5/PEQ ATPIAL, Insight WMX-200.


Good example of "early" CQBR with SOPMOD Block II accessories including SU-231 (EOTech 553) and SU-233 (Insight M3x weaponlight).


Example of a more "modern" CQBR with SOPMOD Block II accessories including the updated SU-231a (EOTech EXPS 3-0) and Insight WMX-200 weaponlight.


Many times certain configurations are common within certain branches/groups. Here a Marine Raider is seen with a CQBR with an AN/PEQ-16 (USMC issued vs. the LA-5/PEQ SOCOM issued ATPIAL) and KAC NT4 suppressor (vs. the current Surefire SOCOM suppressor).

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Building a clone

If you're interested in building a "clone" of a Mk 18 or CQBR equipped M4A1, here is a basic parts list to use as a guide and get you started. This list is not exhaustive and see the * note above regarding personalized accessories.

                       | Mk 18 Mod 0                      | M4A1 CQBR Block I                   | M4A1 CQBR Block II                                      
Lower Receiver         | Mil-spec forged A1               | Mil-spec forged A2                  | Mil-spec forged A2                                      
Stock                  | Gen 1 SOPMOD (Black)             | M4, CAR, SOPMOD, CTR & others       | M4, CAR, SOPMOD, CTR & others                            
Pistol Grip            | A1                               | A2, ERGO & others                   | A2, ERGO & others                                        
Rear Sling Plate       | CQD                              | CQD                                 | CQD                                                      
Upper Receiver         | Mil-spec forged M4 profile       | Mil-spec forged M4 profile          | Mil-spec forged M4 profile                              
Barrel                 | 10.3"                            | 10.3"                               | 10.3"                                                    
Rail                   | KAC RIS                          | KAC RAS                             | DD Mk18 RIS II (FDE)                                    
Rear BUIS              | LMT Fixed                        | LMT Fixed, MATECH, & others         | MATECH, KAC 300m, & others                              
Front Sight            | A2 FSB                           | A2 FSB                              | KAC 99051 BUIS (Taupe)                                  
Front Sling Attachment | FSB Sling Swivel                 | FSB Sling Swivel                    | CQD                                                      
Muzzle Device          | KAC M4QD                         | KAC M4QD                            | SureFire FH-556-RC                                      
Supressor              | None                             | KAC QDSS NT4                        | SureFire SOCOM556-RC (FDE)                              
LAM                    | None                             | PEQ-2                               | LA-5                                                    
Weaponlight            | SureFire M962                    | SureFire M952, M962                 | Insight M3X (Tan), Insight WMX200 (Bronze)              
Optic                  | Aimpoint Comp M2 in Wilcox Mount | Aimpoint Comp M2 in QRP Mount, ACOG | EOTech 553 (Tan), EOTech EXPS3-0 (Tan), ELCAN 1-4x (FDE)

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Link to previous threads

 Previous Mk 18 / CQBR Thread Part I
 Previous Mk 18 / CQBR Thread Part II

Well, we can't be letting this bullshit stop the CQBR signal :D.

Time for an SFMB/RC Update!

It's been just short of 2k rounds since switching to the SFMB and I'm finally starting to see some subtle changes in the wear pattern on the RC. Seems there's some very gradual erosion on the high points between the old 4P erosion channels, but it's very minor and it doesn't appear the "chips" where there's actual baffle penetration have enlarged despite how hard I've been running it.

I originally thought I'd see some minor erosion around the bore, but it's happening so slowly that it's really only started to be apparent recently. Also kinda interesting to note that the 4P erosion channels are starting to fill up with carbon.

Woo, baffle time-lapse:

13,300 (All 4P, prior to the SFMB)
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14,000
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14,500
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15,000
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Overall, I'm extremely happy with the switch and the reduction in erosion has surpassed any expectations I had. I've been running it much harder than I ever did with the 4P and there's barely any sign I've even been shooting it; that's pretty awesome.

There are a few downsides, like carbon being blown into the locking collar threads and possibly a bit more fouling in the action, but the trade-off is more than worth it IMO.

I don't know what any of that means but

Open Notepad (choose "run as administrator"). You can do this by going to Search, typing "Notepad" and then right clicking on Notepad and choosing "Run As Administrator".

Once in Notepad, go to File>Open; at the bottom of the window that pops up, to the right of "File Name" will be "Text Documents (*.txt)". Click the drop-down and select All Files (*.*) and navigate to:

C:\Windows\System32\drivers\etc

Open "hosts" and paste in the IPs/hostname as above. It'll look like this (you can add a comment as I did, or not -- comments are any line beginning with # and will be ignored/aren't part of the config file):



Choose "Save" and you'll now have the DNS for ar15.com resolved locally rather than relying on your ISP DNS server or an external DNS server. This will only work as long as Arfcom still has an active host at those IPs.

Again

I know "not tech" but given events today most relevant. And better than a pic of a CQBR Burro.
Just do this, as well as for those places that are critical to YOU.  Don't go nuts with your hostfile; making it too big will defeat the purpose.  But consider that 2 of the most ginormous DNS servers in use belong to Google, this is a sound precaution.  And resolving to those places will run like a turpentined cat.

Thank you!!

Whoa, whoa, whoa... let's not start talking crazy :\.

@krdt

looks like you have a way to go. he is holding a mk18 with an elcan for the majority of this video

80k rounds and only reworked once

This better not be the case, but I've seen stranger things in the past week.

Nice

How much were these surplus kits?

Anymore coming?

Yeah, don't know what came over me.  Channeling some serious hate for tyrants maybe.
Thanks.  Feel better now.

Have you seen a difference in back pressure, gas to to the face, and a change to your recoil impulse after changing muzzle devices?

Yeah, I saw it; pretty disappointing if I'm being honest. A very generic review with surprisingly few observations of interest and startingly little info/data provided as a result of hitting such a high round count.  

No mention of what sort of erosion he had by 40k or how many baffles he'd penetrated by the time he elected to rebuild (if used hard with mostly pronged mounts, I'd be very surprised if he hadn't burned through multiple baffles by 40k). No observations on performance loss over the life of the can from erosion and/or carbon accumulation, how often he was cleaning it (or the method), nor any mention of if/when he reached a point he was unable to remove a satisfactory amount of carbon/copper accumulation.

Hell, not even an explanation of what finally motivated him to rebuild -- I'm assuming accumulation, but even that isn't made entirely clear.  

Aside from the few passing references to the 80k total and rebuilding at 40k -- a number I consider nearly meaningless since it isn't accompanied by any other relevant data -- the high round count was basically immaterial to the content of the video. I expected he'd have at least one or two interesting insights gleaned as a result of reaching the end of the life of the can nearly twice over; but apparently not. Not to toot my own horn, but I'd submit that I've put out significantly more hard data and useful information after 15k than his review at 80k.

I realize not everyone is as interested in detailed data as I am, but it seems almost ridiculous to make a big deal of doing a review at 80k and then only provide generic information without a single meaningful observation on long-term wear or performance. What's the point? All in all, he could've done the same review after 2-3k and it wouldn't have made any significant difference.

Yeah he kinda just said "built like a tank" and then moved on. Degradation of it's performance over time would've been nice

Gas to the face, no; changes to recoil impulse, no.

It's possible there might be a minor increase in backpressure fouling in the action, but I'm starting to doubt that and think it was almost entirely a result of ammo. Unfortunately, the MD switch corresponded exactly with me switching from 55gr to 62gr bullets and a higher pressure powder charge, which made any initial observations pretty useless. I did have some issues with my safety locking up and the BCG coming close due to hard carbon fouling (which had never been an issue prior to switching), but I've since lowered my powder charge and the issue has disappeared.

I put 400rds through it a couple of days ago and fouling was no more than usual prior to the switch. The main difference that stands out at this point is carbon getting into the locking ring threads.

So basically just something that becomes another routine PM task, yes?  (non-can owner here)

So has anyone run into any issues w/ surplus uppers? It seems there has been allot of them flooding the market and I have an opportunity to snag a pretty cool / rare one so I was just wondering. Maybe @Combat_Diver can shed some light on the process of these upper parts becoming surplus?

I dunno about @Combat_Figer, but perhaps @Combat_Diver can weigh in

Yep, pretty much. A slight bit of a pain because you have to pull the collar apart to clean the threads, but not a terribly big deal.

I'm sure if you left it long enough it'd start to be an issue and require a strap wrench to loosen the collar. So far, I've been pulling it apart and sticking the base in the ultrasonic with the collar removed when it starts getting noticeably sticky.

FML...

I haven’t heard on what Crane is doing. All my excess goes back to Crane.

CD

So it's just your spares and not out of spec/ worn out parts?

Out of spec/worn parts go into the shredder for destruction.  Not cost effective to send busted stuff from Afghanistan to Indiana.

CD

Where are you all sourcing the surplus ones from mainly? Not your specific rare one but in general

Very nice

Where are yall getting these surplus kits?

Thoroughbred Armament.  Big batch is sold out, but you never know when stuff is going to get listed.  Instagram is the best place to keep up to date with them.  Stuff goes quick.

Appreciate all your knowledge!

Attached File


The placement of these numbers seem off (too far forward), has anyone seen anything that would suggest these weren't an attempt to make normal uppers look legit/cooler?

Edit: specifically looking at the top upper there seems to be something blotted out where the numbers are typically found

Attached File

I should have my stamp for my Surefire Socom RC very soon (hopefully). While messing around on Youtube, I came across this video

I'm kind of annoyed that I have to spend $70 on a single steel rod after I just bought the suppressor, a surefire flash hider, a reaction rod, and paid for a stamp. Are these bore rods necessary, or is this just one more thing for Surefire peddle? Thank you in advance.

Thought the same thing. Placement is off, font is off, Missing UID (which could have come off) and within this serial range they are FN uppers

Is there a place to check serial number ranges? I always thought that the numbers were matched to the lowers.

Not that I'm aware. I dont think the serials match the lowers either. Unless you have heard different. I think its just a sequential number assigned as they are assembled and inspected.

Ok just wondering how you were able to determine these numbers went w/ FN. I messaged him so I'm waiting to see what he says but at this point seems like a poor attempt to turn more of a profit on some colt keyholes.

Most new production barrels should have concentric threads unless you bought some no name bottom of the barrel, barrel. Make sure your muzzle device is properly threaded on and the shims mate to the shoulder of the barrel all the the way around and you should be good. I have several suppressors and have never used a rod. I use 3 methods to double check before shooting for the first time.

1. remove the upper from the lower, mount suppressor, look down the business end and you should be able to see clearly from the suppressor all the way out the back of the receiver. No half moon or obstruction, should be a complete circle.

2. Same as above but from the receiver end down through the suppressor - perfect circle.

3. Place the upper on the lower, lock the bolt back and shine a flashlight from the suppressor end cap and it should project a perfect circle on the bolt face. Again, no half moon, a perfect circle.

4. Buy a couple boxes of ammo with the $70.

Been busy, but I finally got a chance to scrub down my Savannah kit.  06/09 cut down Colt gov profile barrel and an "SDI" bcg(I've been told Sabre Defense).  Also I know nothing about how DD manufactures their rails, but I found it interesting that the lot numbers are the same, but the upper and lower piece differ by 2 days.  23OCT07 VS 25OCT07

Hopefully I'll get it put together tomorrow.  Should pair nicely with a salty police trade in Colt AF upper I have.

I only do a visual inspection.

Attach the can, remove the BCG, and hold the upper up to a light background looking down the bore from the rear. Any serious misalignment is going to be immediately apparent as described above, i.e. a visible 1/4-1/2 moon. However, you also want to look for any less obvious misalignment by visually centering the bore and then slowly moving the rear of the upper to the right, back to center, to the left, back to the center, and so on; then the same up and down. Even if you have no indication of an obstruction when centered, you still want to verify one side isn't noticeably closer to the center than the other (you can still have misalignment short of a full-on visible obstruction).

You can also look from the muzzle end and verify the bore is centered inside the can -- again you don't want it to be biased more or less in any direction.

To summarize, I don't feel alignment rods are really necessary, but I suppose it comes down to how much faith you have in the calibration of your Mk-1 Eyeball.

Have seen a couple with that number placement.

Edit: Don't think the bottom pic has the forward number placement

That bottom picture is soooo confusing to me.

It was COTS testing for DMs. Lol

But that top pic is the first I've seen if it in that location. Contacted the seller and he is going to forward some more photos of the #s that forward location.

Haven't seen those pics before, good find! Font is still not the same though on the uppers in question. Doesn't seem as thick

Attached File

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Navy guns from 16'

Todays range training, 600 rds of 5.56 and 260 rds of 9mm
Attached File


CD

Jeez, that’s like $700 worth of ammo here stateside right now.

You don't have to spend $70.

Get one from McMaster-Carr for $5.12. The other ones are a scam.

8893K193     Tight-Tolerance Oil-Hardening O1 Tool Steel Rod, 0.2188" Diameter, 3 Feet Long   1  $5.12

*ETA: if anyone wants the size for .300 BLK:
8893K219     Tight-Tolerance Oil-Hardening O1 Tool Steel Rod, 0.2969" Diameter, 3 Feet Long   1  $6.67